A roller vane pump has rollers that fit into openings within a rotor. As the rotor rotates it drives the rollers around the inside of a non-rotating cam ring. The rollers roll on the inside of the cam ring and will slide on the rotor face, or the roller will be fixed against the rotor face and will slide against the cam ring. Then the surface that has the lowest coefficient of friction will be the surface on which sliding will occur.
The pump is ported through a port plate under the rollers to allow hydraulic fluid to flow into and out of the pump. The rotor center line is offset from the cam ring center line to create two volumes, one that is expanding in the direction of rotation and one that is contracting in the direction of rotation. The expanding volume is the inlet/low pressure side and the contracting volume is the outlet/high pressure side. Two transition zones exist that are not ported to either the high pressure or low pressure side. The rollers act as seals in the transition zone between the high pressure and low pressure chambers to prevent fluid transfer from high pressure to low pressure. There is always some point in the pump where transition occurs between high pressure and low pressure. In the transition zone the roller is loaded by high pressure against the rotor face and against the inside of the cam ring. The relatively small radius of the roller against the larger radius of the cam ring or the flat face of the rotor causes high compressive stress when the roller is pressure loaded in the transition zone.
There are two types of transitions, the first is transition from high pressure to low pressure. In this area the roller is loaded against the trailing side of the rotor face. In the second transition, or the low pressure to high pressure transition, the roller is loaded against the leading rotor face.
One problem with this system is that the sliding that occurs between the roller and the rotor, or cam ring, at high rotation speeds, when added to a high compressive load, limits the operating speed and pressure for the roller vane pump. Consequently, if higher speeds and pressures are attempted, wear occurs between the roller and the cam ring, or between the roller and the rotor face. This results in wear and limits the pump life, and effects pump efficiency.
Because of the problems in the art, there is a need in the art to have a roller vane pump that maintains a low coefficient of friction between the rotor and the roller and a higher coefficient of friction between the roller and the inside of the cam ring. There is also a need to reduce the amount of wear on a roller vane pump. There is a need in the art to provide a roller vane pump that will protect an advancing and trailing rotor face, thus it will be able to rotate clockwise and counterclockwise using the same roller and rotor components.
Therefore, it is a primary object of the present invention to provide a roller vane pump that maintains a low coefficient of friction between the rotor and roller by introducing a slipper as an intermediator, and high coefficient of friction between the roller and the inside of the cam ring.
A further object of the present invention is to provide a roller vane pump that reduces the wear of the pump when it is operated at high speeds causing the pump to have a longer life and improved efficiency.
Yet a further object of the present invention is to provide a roller vane pump designed that uses a roller with a slipper that will protect the advancing and trailing rotor face.
Another object of the present invention is to protect the advancing and trailing rotor face by having a design that can be used with clockwise and counterclockwise rotation using the same slipper, roller, and rotor components.
These and other objects, features, or advantages of the present invention will become apparent from the specification and claims.